Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CREATING FREQUENT APPLICATION-CONSISTENT BACKUPS EFFICIENTLY
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BACKGROUND
Background and Relevant Art
[0001] As computerized systems have increased in popularity, so have the needs
to store
and backup electronic files and other communications created by the users and
Applications associated therewith. In general, computer systems and related
devices create
files for a variety of reasons, such as in the general case of creating a word
processing
document in a work setting, as well as creating a file used for more
sophisticated database
purposes. In addition, *many of these documents can include valuable work
product, or
sensitive information that should be protected. One will appreciate,
therefore, that. there
are a variety of reasons why an organization will want to backup electronic
files on a
regular basis, and thereby create a reliable restoration of an originally
created file when
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needed.
[0002] Despite some of the conveniences afforded by many conventional backup
systems,
the mechanisms used by many conventional systems are often less efficient than
optimal.
For example, the ability to create an application-consistent backup can be an
important
component of some backup systems. An application-consistent (as well as a file
system-
consistent) backup is basically a backed-up set of data that are consistent in
file state for a
particular point in time. For example, if a backup administrator copied all
data on a given
production server volume, even as the data may be in the process of being
written-to or
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updated, the file state of the corresponding backup copy may not necessarily
be consistent
for a single point in time. Creating an application-consistent backup,
therefore, generally
involves the additional effort of reconciling file state.
[0003] Nevertheless, one can appreciate that there can be any number of
difficulties
associated with creating application-consistent data backups: For example,
conventional
mechanisms for creating a backup generally involve an application program,
such as a
backup component of a mail or database application program, calling one or
more backup
and/or restoration Application Program Interfaces ("APIs"). In particular, the
backup
component might tell the APIs to freeze writes to certain specified disk data
on the
production server, and then create a backup copy (i.e., "replica") of the
data.
Unfortunately, there is generally no simple way for backup components to
describe their
data to the backup APIs at the production server. Further complicating this
difficulty is
the fact that there can sometimes be a large number of backup APIs that may
need to be
referenced during a backup process.
[0004] In addition, the fact that a particular application that created
certain data is
requesting the backup services often implies that less than all of the
production server data
might be backed up at any given time. For example, conventional backup
mechanisms are
often application-specific with respect to the data being backed-up. Such
application-
specific backup approaches often involve running multiple instances of the
given
application during the backup process. One will appreciate, however, that
running
multiple instances of a given application can be inefficient for a number of
reasons,
whether from a cost or resource expenditure perspective.
100051 Furthermore, even using applications to provide backup services can be
somewhat
ineffective since application-specific backups generally do not provide point-
in-time
copies of the application data without significant resource expenditures. This
can mean
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that an application may not be able to provide an application-consistent point-
in-time
backup with high frequency (thus providing highly granular recovery points)
without
overloading both the production server and the backup server. Thus,
conventional
backups performed by a particular application typically cannot provide a "hot
standby" of
point-in-time backups that are only a few minutes old.
10006] This general lack of granular configurability can extend to a wide
variety of other
issues in backup systems. For example, conventional backup systems can be
difficult to
configure for types of files, specific folders, or folder locations on a
particular volume.
Thus, there can be difficulties associated with having conventional backup
systems backup
production server data with better granularity than just an entire one or more
volumes, or
just entire files, as opposed to backing up just those portions of the files
that have actually
been modified. These and other similar problems often mean that the production
server
and backup server are configured to copy and transfer more data between them
than
necessary, which of course can affect system performance and network
bandwidth. In
particular, the production server may be copying and transferring file data
that have not
changed, as Well as entire files that have only changed only in small part.
Because of this,
the backup server may also need to devote more storage capacity than necessary
for
backing up the production server data.
[0007] One will appreciate, therefore, that each of the afore-mentioned
factors (or
combinations thereof) can negatively affect Recovery Point Objectives ("RPO"),
which
generally refer to how far back in time data need to be recovered in order for
an
organization to re-launch operations after a disaster. The afore-mentioned
factors can also
negatively affect Recovery Time Objectives (RTO), which generally refer to how
much
time will pass after a disaster before the data necessary for re-launching
operations can be
recovered. That is, conventional backup systems are generally ill-equipped to
provide
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relatively high recovery points, particularly in a relatively quick amount of
time without
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undue burdens on system resources.
[0008] Present backup systems, therefore, face a number of difficulties that
can be
addressed.
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BRIEF SUMMARY
[0009] Implementations of the present invention solve one or more problems in
the art
= with systems, methods, and computer program products configured at least
in part to
optimize recovery point objectives and recovery time objectives in backup
systems. For
example, in at least one implementation, resource savings at a production
server can be
achieved by monitoring changes to production server volumes with a volume
filter driver.
In addition, network bandwidth and backup server resources can be used
efficiently by
transferring primarily just the incremental changes (e.g., bytes, or byte
ranges of changes)
to a backup server since the last replication cycle. As . will be appreciated
more fully
herein, such optimizations can provide the ability to backup production server
data in a
virtually continuous (or near continuous) fashion without significant drains
on production
server resources, backup server resources, and/or network bandwidth concerns.
[0010] For example, a method from the perspective of a production server of
replicating
production server data in a virtually continuous, consistent fashion can
involve sending a
copy of volume data from one or more volumes of a production server to a
backup server.
In such a case, the sent copy of data for the volume(s) will generally be
consistent (i.e.,
application-consistent or file system-consistent) for a first instance of
time. In addition,
the method can involve identifying one or more changes to the volume data via
one or
more volume log files. The method can further involve, upon identifying a
replication
cycle event, saving the one or more data changes in the one or more volume log
files.
Generally, the one or more data changes will also be consistent for a second
(i.e.,
subsequent) instance of time. Still further, the method can involve sending to
the backup
server a copy of the one or more changes. As such, the backup server will have
a copy of
data of the one or more volumes, where the data are valid for a first instance
of time and a
second instance of time.
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[0011] By contrast, a method from the perspective of a backup server of
replicating
production server data in a virtually continuous, consistent fashion, can
involve receiving one
or more volume backups from a production server. In such a case, the one or
more volume
backups are consistent for an initial instance of time. The method can also
involve receiving
one or more application-consistent backup updates, at least one of which is a
consistent update
to at least one of the one or more volume backups for a subsequent instance of
time. In
addition, the method can involve receiving a recovery request for data that
are valid in
accordance with the subsequent instance of time.
[0012] Furthermore, the method can also involve identifying the requested data
for the
subsequent instance of time at one or more backup server volumes. In such a
case, the
requested data include at least a portion of the at least one application-
consistent backup
update. In addition, the method can involve sending the requested data that is
valid for the
subsequent instance of time to the production server.
[0012a] According to one aspect of the present invention, there is provided at
a production
server in a computerized environment in which one or more production servers
backup data to
be protected on one or more volumes at one or more backup servers, a method of
replicating
production server data in a virtually continuous, consistent fashion, such
that recent data can
be easily recovered from the backup server, comprising the acts of: at a first
instance of time,
creating a copy of data for one or more volumes from a production server, the
copy
corresponding to a full baseline of the data for the one or more volumes;
sending the copy of
the data for the one or more volumes from the production server to a backup
server, wherein
the data is consistent for the first instance of time; subsequent to the first
instance of time,
storing an indication for each of one or more changes to the data on the one
or more volumes,
the indications being stored in one or more bitmaps that are stored in
volatile memory on the
production server, wherein at least one of the one or more changes includes a
change to a file
path of a file corresponding to any of the one or more data changes at the
production server,
such that the file path at the production server is different from a path to
the file at the backup
server; upon identifying a replication cycle event, saving the one or more
bitmaps to one or
more log files that are stored in persistent storage of the production server,
wherein the one or
more data changes are consistent for a second instance of time; deleting the
one or more
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bitmaps from the volatile memory; using the indications from the one or more
bitmaps to
identify the one or more data changes for the one or more volumes; correlating
the paths for
the file at the production server and at the backup server, such that new
changes to the file can
be sent to the backup server with a change in the path for the file, wherein
correlating the
paths comprises: scanning an update sequence number (USN) journal at least a
first time to
cache the change in file path at the production server; scanning the USN
journal at least a
second time to identify the initial file path at the production server; and
computing an adjusted
path to the file at the backup server based on the first and second scans; and
sending to the
backup server a copy of the one or more data changes for the one or more
volumes, such that
the backup server has a copy of data for the one or more volumes that are
valid for a first
instance of time and a second instance of time.
[0012b] According to another aspect of the present invention, there is
provided at a
production server in a computerized environment in which one or more
production servers
backup data to be protected at one or more backup servers, a computer storage
media having
computer-executable instructions stored thereon that, when executed, cause one
or more
processors at the production server to perform a method of replicating
production server data
in a virtually continuous, application-consistent fashion, such that recent
data can be easily
recovered from the backup server, comprising the acts of: at a first instance
of time, creating
a copy of data for one or more volumes from a production server, the copy
corresponding to a
full baseline of the data for the one or more volumes; sending the copy of the
data for the one
or more volumes from the production server to a backup server, wherein the
data is consistent
for the first instance of time; subsequent to the first instance of time,
storing an indication for
each of one or more changes to the data on the one or more volumes, the
indications being
stored in one or more bitmaps that are stored in volatile memory on the
production server,
wherein at least one of the one or more changes includes a change to a file
path of a file
corresponding to any of the one or more data changes at the production server,
such that the
file path at the production server is different from a path to the file at the
backup server; upon
identifying a replication cycle event, saving the one or more bitmaps to one
or more log files
that are stored in persistent storage of the production server, wherein the
one or more data
changes are consistent for a second instance of time; deleting the one or more
bitmaps from
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the volatile memory; using the indications from the one or more bitmaps to
identify the one or
more data changes for the one or more volumes; and correlating the paths for
the file at the
production server and at the backup server, such that new changes to the file
can be sent to the
backup server with a change in the path for the file, wherein correlating the
paths comprises:
scanning an update sequence number (USN) journal at least a first time to
cache the change in
file path at the production server; scanning the USN journal at least a second
time to identify
the initial file path at the production server; and computing an adjusted path
to the file at the
backup server based on the first and second scans; and sending to the backup
server a copy of
the one or more data changes for the one or more volumes, such that the backup
server has a
copy of data for the one or more volumes that are valid for a first instance
of time and a
second instance of time.
[0013] This Summary is provided to introduce a selection of concepts in a
simplified form
that are further described below in the Detailed Description. This Summary is
not intended to
identify key features or essential features of the claimed subject matter, nor
is it intended to be
used as an aid in determining the scope of the claimed subject matter.
[0014] Additional features and advantages of exemplary implementations of the
invention
will be set forth in the description which follows, and in part will be
obvious from the
description, or may be learned by the practice of such exemplary
implementations. The
features and advantages of such implementations may be realized and obtained
by means of
the instruments and combinations particularly pointed out in the appended
claims. These and
other features will become more fully apparent from the following description
and appended
claims, or may be learned by the practice of such exemplary implementations as
set forth
hereinafter.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to describe the manner in which the above-recited and other
advantages
and features of the invention can be obtained, a more particular description
of the
invention briefly described above will be rendered by reference to specific
embodiments
thereof which are illustrated in the appended drawings. Understanding that
these drawings
depict only typical embodiments of the invention and are not therefore to be
considered to
be limiting of its scope, the invention will be described and explained with
additional
specificity and detail through the use of the accompanying drawings in which:
[0016] Figure lA illustrates an architectural overview diagram in accordance
with an
implementation of the present invention in which a production server creates
incremental
application (or file system)-consistent backups and sends those backups to a
backup
server;
[0017] Figure 1B illustrates an overview diagram in accordance with an
implementation
of the present invention in which a volume filter driver monitors changes to a
volume
using system memory and one or more physical disks; and
[0018] Figure 2 illustrates flowcharts of methods comprising a sequence of
acts performed
from the perspective of a production server and a backup server in accordance
with
implementations of the present invention.
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DETAILED DESCRIPTION
[0019] The present invention extends to systems, methods, and computer program
products configured at least in part to optimize recovery point objectives and
recovery
time objectives in backup systems. For example, in at least one
implementation, resource
savings at a production server can be achieved by monitoring changes to
production server
volumes with a volume filter driver. In addition, network bandwidth and backup
server
resources can be used efficiently by transferring primarily just the
incremental changes
(e.g., bytes, or byte ranges of changes) to a backup server since the last
replication cycle.
As will be appreciated more fully herein, such optimizations can provide the
ability to
backup production server data in a virtually continuous (or near continuous)
fashion
without significant drains on production server resources, backup server
resources, and/or
network bandwidth concerns.
[0020] As will be appreciated more fully from the following specification and
claims,
implementations of the present invention can meet a wide range of "recovery
time
objectives" by refreshing the backup server with a "full snapshot" of
production server
data. In addition, implementations of the present invention include a volume
filter driver
that can be implemented at the production server. As will be appreciated more
fully
herein, the volume filter driver can be configured to monitor changes to bytes
(and or byte
blocks) on production server volume(s). The production server can then be
configured to
send an entire snapshot (or backup copy) by sending only those changed bytes
(or byte
blocks) to the backup server. As such, use of a volume filter driver can
mitigate the
burden on resources that might otherwise be consumed when moving a full
snapshot of
production server data to a backup server.
[0021] Furthermore, and as a result of these and other features, the
production server can
provide a backup server with virtually continuous backups of several
"consistent" (i.e.,
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application-consistent and/or file system-consistent) snapshots (i.e., initial
backup and
subsequent shadow copies) that are spaced close together in time. In addition,
since each
update to the backup is application-consistent (and/or file system-
consistent), or valid for a
specific instance of time, the difference between each update will also be
application-
consistent. As such, implementations of the present invention provide a user
with the
ability to recover a wide range of application-consistent data (e.g., from the
file level,
database level, and even entire production server level) with fairly high
granularity (e.g.,
only a few minutes old) with much less burden than otherwise might be needed.
[0022] Generally, there are a variety of ways in accordance with
implementations of the
present invention for implementing continuous, consistent backup services. In
at least one
very basic sense, creating a consistent backup includes creating a baseline
copy (e.g., 145)
of one or more volumes (e.g., 175), and then supplementing that baseline copy
with
incremental, consistent updates (e.g., 150, 155) to the one or more volumes.
For example,
Figure 1A shows that production server 105 creates at least one baseline
backup copy
(e.g., 145) of data on selected volume(s) 175. In addition to simply creating
the baseline
copy 145, a backup administrator in system 100 might use any number or type of
mechanisms to make copy 145 consistent.
[0023] In one implementation, the backup administrator might use a replica
agent (not
shown), installed at backup server 110 and/or at production server 105 to
guide replication
processes. During a replication cycle, for example the replica agent might be
configured to
instruct any one or more appropriate application writers on production server
105 to
momentarily hold write activities on any one or more volumes (e.g., a database
may span
several volumes, and several applications can use the same volume with
different
replication schedules) for a single point in time. (For a file share backup,
an application
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writer may not even be involved at all.) This allows the replica agent to
thereby create a
single point-in-time backup (i.e., "shadow copy") of the one or More volumes.
[0024] The replica agent may also provide instructions to each application
writer to
perform certain functions on their data of interest, to thereby ensure that
all data and
metadata are consistent for the point-in-time of the replication cycle. For
more simple
applications that may not have an application writer or corresponding plug-in
associated
therewith, the replica agent might be configured to simply instruct those
applications to
freeze or shut down during the replication cycle. The aforementioned agents,
components,
and functions for creating consistent backups can be provided in at least one
implementation in the MICROSOFT environment, for example, with a Volume Shadow
Copy Service ("VSS").
[0025] In any event, having frozen the writes of interest to a particular
volume (or
volumes) and for a particular instance in time, production server 105 can then
make and
send a copy of the volume(s) (or alternatively only those selected folders,
files, or file
types) of interest. For example, Figure lA shows production server 105 can
provide this
initial baseline copy 145 to backup server 110. Generally, production server
105 can
provide the baseline copy 145 any number of ways. In one implementation, for
example,
production server 105 simply sends copy 145 over a network connection. In
other
implementations, such as where network bandwidth may be more limited, a backup
administrator can transfer the volume copy to tape (or another intermediate
storage node ¨
not shown) and later connect that tape to backup server 110. However
performed,
production server 105 provides backup server 110 with at least one consistent
baseline
copy of all the data (i.e., valid for time "to,") for the volume, folder,
file, or set of files of
interest that shares the same replication cycle.
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[0026] After providing one or more baseline copies of the one or more
production
server(s) volumes, backup server 110 can continue to receive updates to the
baseline
backup(s). For example, backup server 110 can continue to backup production
server 105
on a wide variety of configurable replication schedules, such as those ranging
in the order
of about 5-10 minutes, 10-15 minutes, 15-30 minutes, or the like. Generally,
the level to
which the backup administrator configures the replication cycles will be the
level of
granularity to which one can access a particular "recovery points."
[0027] As previously discussed, ordinarily a relatively high level of
granularity in the
accessibility of point-in-time backups could be prohibitively resource-
expensive for some
backup systems. Thus, to create the above-mentioned level of granularity of
"recovery
points) without necessarily compromising the "time taken to recover" (e.g.,
without
incurring significant overhead), implementations of the present invention can
provide a
number of important components and functions.
[0028] In one implementation discussed more fully hereinafter, for example, a
volume
filter driver 115 can be used to monitor iterative changes to any of the one
or more
volumes (e.g., 175) at production server 105, with either in-memory bitmaps,
or by
marking particular changed bytes (or byte blocks) in a volume log file on
disk. Generally,
a volume filter driver (e.g., 115) will be independent of how hardware or
software-based
"snapshots" are implemented on production server 105. One will appreciate,
however,
that a volume filter driver 115 is not necessarily required, and similar
functions may be
performed by other components, as also discussed herein. In additional or
alternative
implementations production server 105 can also monitor changes to the volume
(e.g.,.
changes to files 120, 125, 130, etc.) through the use of conventional shadow
copy
monitoring mechanisms, and/or Update Sequence Number journals (i.e., "USN
journal" '
140), or the like. With particular respect to the MICROSOFT operating
environment, for
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example, such components are provided through combined use of a Volume Shadow
Copy
Service ("VSS") and a USN journal.
[0029] Generally, a volume log file (e.g., 135) can comprise all of the
changes to a volume
during a specific replication cycle (e.g., volume offset, length of data
change) for each
write to the volume, and/or in-memory bitmap of changes. When a specific
replication
cycle occurs, an existing volume log file (e.g., 135) is frozen, and a new
volume log file
(not shown) can be created to gather changes for the next replication cycle.
In one
implementation, volume level changes can be sent directly to backup server
110, without
any additional correlating information. Corresponding updates sent to backup
server 110
might then be applied into the replica as "byte n" (or "byte block n changed
to n+1"). In
-additional or alternative implementations, volume data at production server
105 can also
be correlated with USN journal (or related component) 140 information.
[0030] In particular, a USN journal (e.g., 140) comprises time-stamped
information of
such activities with respect to the file name data in the file system.
Components similar or
identical to USN journal 140 are also referred to as change filters, or change
journals, or
the like. Specific reference to a "USN journal 140" herein, therefore, is made
primarily by
way of convenience. In any event, and with reference to file system activity,
production
'server 105 can combine volume log file (e.g., 135) data and change journal
data (e.g.,
USN journal 140) to correlate the time, type of activity, and file name, etc.
of the various
writes to volume 175.
[0031] Along these lines, USN journal 140 can also be used in conjunction with
volume
log file 135 to correlate such things as the address of a particular byte or
"byte block"
change (as well as corresponding files for the change). In particular, each
file on a volume
can be thought of as an open set of addressable bytes, as well as an open set
of addressable
fixed-length byte blocks. In some cases, monitoring and transferring byte
blocks (rather
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than individual bytes) can be a more efficient way to monitor and transfer
changes, as well
as determine how much space may be needed for backup purposes. In particular,
this is in
part since byte blocks represent a level of granularity that is usually
somewhat less than
that of an entire file, but greater than that of a single byte. As such,
Figure lA shows that
production server 105 logs the various byte or byte block changes to its files
to be
protected.
0032] For example, Figure lA shows that production server 105 logs that bytes
(or "byte
blocks") 121, 122, arid 123 of file 120 have changed (e.g., 120 is a new file)
since the last
replication cycle *(e.g., last 5, 10, 15, 20, 25, or 30 minutes, etc.).
Similarly, although file
125 comprises bytes (or byte blocks) 127, 128, and 129, only bytes 128 and 129
have
changed; and where file 130 comprises bytes 131, 132, and 133, only byte 133
has
changed since the last replication cycle. Generally, production server 105 can
log these
changed bytes in a read-only shadow copy of the volume, folder, or relevant
files.. As
previously mentioned, production server 105 can also store these changed bytes
for a
volume log file as in-memory bitmaps (e.g., using a bit per block of data on
the volume)
that are later passed to physical disk during replication. However logged or
monitored,
and at an appropriate time (i.e., the next replication cycle), production
server 105 can then
prepare only these file changes (i.e., 121, 122, 123, 128, 129, 133, etc.) to
be sent to
backup server 110.
[0033] In this particular example, the changes (i.e., 121, 122, 123, 128, 129,
133, etc.) are
each valid for the most recent point-in-time (i.e., "ti"), and thus consistent
(i.e.,
application-consistent or file system-consistent). Notably, since these bytes
(or byte
blocks) represent the difference between two consistent point-in-time backups,
the
application of these bytes (or byte blocks) at backup server 110 can also be
consistent.
After identifying these data changes, production server 105 can send these
changes as
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updates 150 (for time t1) to backup server 110. Similarly, production server
105 can
identify and send each next set of incremental data changes (i.e., data
changes logged for
one or more volumes) in a next incremental update for the next replication
cycle. For
example, Figure 1A also shows that production server 105 prepares and sends
update 155
(for time t2) to backup server 110, and so on.
[0034] One will appreciate that from the point at which production server 105
reads the
changed data and prepares message 150, there may be additional changes to the
volume
data, which could make the data being read otherwise inconsistent (i.e.,
consistent for time
"ti" and valid for a subsequent time). As previously discussed with respect to
baseline =
copy 145, therefore, a volume shadow copy service (or other VSS-like
mechanism) can be
used in at least one implementation to read data only for the frozen,
particular instance in
time, and not any changes subsequent thereto. This can help ensure that
snapshot updates
150 (as well as 155, etc.) are consistent up to the indicated instance of time
at which
snapshot (also referred to as backup update or update) operations commenced.
[0035] Upon receipt, backup server 110 can store each backup and corresponding
update(s) in a particular replica volume. In one implementation, backup server
110 stores
the backups and updates in the same volume allocation of the same storage
medium. In
other implementations, backup server 110 (and/or additional backup servers or
storage
nodes) can store the backups and corresponding updates on separate volumes,
and even on
separate storage media, however desired by the backup administrator.
[0036] In some cases, and due to the nature Of the virtually continuous,
iterative backups
of production server 105, a backup administrator may need to synchronize a
number of
aspects of the data with production server 105 data. For example, there may be
cases of
failure during a replication cycle, and/or over several replication cycles,
such as may be
due to network outage, log overflows (e.g., USN journal wrap, etc.). In one
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implementation, therefore, a backup administrator can perform a validation or
correction
by creating a new baseline full snapshot (e.g., similar to 145) of production
server 105.
The backup administrator can then perform (e.g., via production server 105) a
checksum
comparison (or other validation) between the a snapshot of the data on
production server
105, and the data on backup server 110. Any errant data on backup server 110
can then be
fixed, if necessary.
[0037] With particular respect to WINDOWS operating components, for example,
this
checksum can be performed in at least one implementation using Remote
Differential
Compression ("RDC") used in WINDOWS SERVER 2003. In some cases, use of an
RDC type of mechanism may be preferable in a Wide Area Network ("WAN")
environment. In another implementation, such as may be preferable in a Local
Area
Network ("LAN"), the backup administrator can divide each file in a snapshot
into sets of
"chunks" (e.g., byte blocks) and then compute checksums for each chunk.
[0038] In any event, due in part to the level of replication granularity
provided by
implementations of the present invention, if a user requests a particular
version of a file (or
other data representation) that is only a few minutes old (e.g., needed from a
recent
personal computer crash), the user can send a request to backup server 110 for
that
particular version of a file. For example, a user might request a particular
copy of file 120
that was valid as of 5 minutes ago (e.g., "to," or before updates 121, 122,
123). Similarly,
an administrator might request (not shown) an entire reproduction of volume or
volumes
175.
[0039] Upon receipt of the request, and depending on the nature of the
request, backup
server 110 can then find the requested data as appropriate. For example, with
respect to
basic file-system data, each update of volume 175 could contain a full copy of
requested
data. Thus, backup server 110 might only need to identify the time requested
by the user,
CA 02649404 2008-10-15
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identify the data within the. corresponding update for that time, and then
provide a copy of
that data back to the user (e.g., recovery message 160).
[0040] In other cases, such as with mail or other types of database
application data, each
incremental update (e.g., 150, 155) received by backup server 110 might only
contain an
incremental update for the requested data. Thus, backup server 110 could be
configured to
play back each incremental update from the requested recovery point back to
the last
baseline full. Backup server 110 can then combine the requested data
identified during
playback (e.g., 145, 150, 155, or to...), until reaching the time specified in
the request.
When all relevant data from the original backup and corresponding updates are
combined
and prepared, backup server 110 can then send the recovery response (e.g.,
160), which is
valid pursuant to the requested time. For example, Figure lA shows that backup
server
110 sends response 160, which indicates that the recovered data are valid for
time "t1."
[0041] In the foregoing implementation, the backup server 110 may therefore
need
application support to playback the incremental updates. In another
implementation, the
baseline full copy and any corresponding incremental updates between the
baseline full
and the requested point in time can simply be copied back to production server
105. A
corresponding application writer (e.g., an application writer within a shadow
copy service
framework) at production server 105 can then playback the logs on the full
backup.
[0042] Generally, the time that elapses between the request for particular
data and the
corresponding response can be a function of at least two parts:
1. Time to transfer the data from back-up server 110 to production server 105;
and
2. Time for backup server 110 (e.g., via a relevant backup agent) to complete
the
recovery.
Of course, the time to transfer data from target to source is generally a
function of the
network bandwidth available, as well as disk speeds and resource usage at
backup server
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110 and production server 105. By contrast, the time to create a particular
recovery is
typically a function of the time required to recover a full copy of the
production server
data from a given baseline, and the time required to identify and play back
accumulated
updates (e.g., "tn_i") accumulated from the baseline in order to recover a
specific point in
time. One will appreciate, therefore, that recovery time can be greatly
enhanced by
limiting the amount of updates backup server 110 (or production server 105)
has to play
back for any given recovery request, such as by creating periodic baseline
full copies (e.g.,
145).
[0043] As previously mentioned, one way of limiting the amount of incremental
updates
that backup server 110 might need to replay can involve creating a new "full"
baseline
snapshot periodically. Since creating and sending a new, full snapshot to
backup server
110 can be resource-expensive (e.g., network bandwidth, production server 105
resources,
and the amount of backup server 110 disk space needed) in some cases,
implementations
of the present invention also provide for the creation of "intelligent full
snapshots." These
intelligent, full snapshots are effectively a baseline demarcation of a
predetermined point
in time. For example, every predetermined period, such as every two weeks,
backup
server 110 can roll two weeks worth of incremental updates (e.g., 150, 155,
etc.) together
with the last baseline copy of data (e.g., 145, or newer), and thus create
essentially a new
"to" copy of production server 105 data.
[0044] In order to roll each of these incremental updates together
efficiently, backup
server 110 can be configured to monitor all writes to production server 105
volume since
the last full snapshot. In at least one implementation, for example, backup
server 110
implements volume filter driver 115 at production server 105 to monitor
changes to the
volume (i.e., one or more volumes), and store those writes in production
server 105
memory 170 during each replication cycle. For example, Figure IA (see also
Figure 1B)
17
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shows that volume filter driver 115 interfaces between volume 175 and memory
170 on
production server 105. As will be understood more fully in Figure 1B, each
time a change
is made to volume data, volume filter driver 115 can record that change (or
set of changes)
in a volume log file 135. In at least one implementation, these changes are
recorded in
system memory 170 as an in-memory bitmap (e.g., 117a) for each of the one or
more
volumes. When production server 105 is ready for a particular replication
cycle, volume
filter driver 115 can then pass all the in-memory bitmaps to volume 175, and
production
server 105 can then send the corresponding data to backup server 110.
[0045] For example, Figure 1B shows that memory 170 has been used to gather
snapshot
data corresponding to various in-memory bitmaps. In particular, Figure 1B
shows that
volume filter driver 115 identifies certain file changes (i.e., file changes
121, 122, 123,
etc.), and subsequently stores these changes as corresponding in-memory
bitmaps 193,
195, etc. in memory allocation 190a. In this particular example, volume filter
driver 115
stores all changes to the corresponding one or more volumes since the last
replication
cycle (i.e., snapshot 185a ¨ "t2"), and, as such, each bitmap 193, 195, etc.
is valid for the
most recent instance of time in the corresponding snapshot (i.e., 190a,
snapshot "t3").
[0046] When the replication cycle is triggered, such as due to instructions
received from a
replica agent, volume filter driver 115 transfers all bitmaps for snapshot
190a (i.e., bitmaps
193, 195, etc.) to the appropriate volume 175 allocation 190b. For example,
Figure 1B
shows that memory snapshot portions 180a and 185a have been emptied since the
replication cycle for which they were generated has already passed.
Furthermore, the
corresponding volume 175 allocations 180b, 185b, etc. now contain "all
bitmaps" 183,
187 that were previously stored in memory portions 180a, 185a, respectively.
Ultimately,
when a snapshot corresponding to the set of bitmaps is deleted, the bitmaps
(e.g., 183,
187) can remain on the volume (e.g., 175).
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[0047] These in-memory bitmaps (e.g., 193, 195) can be created and implemented
a
number of different ways. In one implementation, for example, backup server
110 takes a
shadow copy snapshot (e.g., snapshot 150) of the production server 105 volume,
an
Input/Output Control ("IOCTL") can be sent to the shadow copy provider
(software or
hardware) . This IOCTL can be intercepted by volume filter driver 115 to split
the active
bitmap. In response, and during creation of the shadow copy, volume filter
driver 115
synchronizes the split by creating a frozen set of bitmaps (e.g., 180a/189b,
185a/185b) and
a new active set of bitmaps (e.g., 190a/190b). In another alternative
implementation, an
entity that is capable of harvesting the shadow copy diff area (e.g., VSS diff
area) could be
aware of the volume level changes and also aware of the USN/file system. As
such, this
entity could provide an abstraction that would give the set of changed files
and the set of
changes in the files. An appropriate replication or backup application can
then use this
infrastructure for achieving replication.
[0048] When a replication cycle is triggered, volume filter driver 115 passes
the frozen
bitmaps to disk in order to reduce memory 170 usage. Volume filter driver 115
can also
expose one or more IOCTLs that can be queried for all the changes that
occurred since the
most recent snapshot (e.g., "t11..1"). In one implementation, querying these
IOCTLs returns
all the bitmaps that have been accumulated since the most recent snapshot. One
will
appreciate that using in-memory bitmaps as described herein to monitor changes
can be
=
very efficient, at least in part since in-memory bitmaps tend not to affect
production server
105 resources significantly.
[0049] In an alternative implementation, and to identify each of these
monitored changes,
backup server 110 can also identify the set of files that are changed using,
for example
USN journal 140 (or using other monitored file metadata). Backup server 110
(or relevant
component) can then query the production server 105 file system for the file
extents that
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each changed file occupies. An intersection between the file extents queried
from. the file
system and the file extents that volume filter driver 115 reports can provide
the extents of
the file that have changed since the last replication cycle, and thus allow
certain files (e.g.,
database files) to be excluded from certain replication processes. Backup
server 110 (or
relevant component) can then repeat this process for each changed file (either
as reported
by a USN journal or by a similarly-configured metadata document).
[0050] With particular respect to using a USN journal to monitor changes at
production
server 105, one will appreciate that a File Reference Number ("FRN") at
production server
105 might not match with the FRN for the same file stored at backup server
110. Thus, in
order to send the monitored changes from production server 105 to backup
server 110, it
may be important in some cases to compute a correct, matching path to the
particular
changed file. For example, a volume might have the following changes, which
involve
modifying a path at production server 105 for file "y.txt":
1) Modify C:\a\b\c\y.txt
2) Rename C:\a\b to C:\p\q\r
3) Modify C:\p\q\r\b\c\y.txt
4) Delete C:
In the example illustrated immediately above, original path "a\b" at
production server 105
is renamed as path "p\q\r," and directory "\a" of the original path is
deleted. This leaves
the path at production server 105 for file "y.txt" to be
"C:\p\q\p\r\b\c\y.txt." Nevertheless,
these path changes for "y.txt" at production server. 105 may not automatically
result in
changes to the path at backup server 110. In particular, the path to y.txt at
backup server
110 will generally remain "a\b\c\y.txt."
[0051] At the time of a snapshot, production server 105 might also record into
the USN
Journal the following changes shown below for example records 1-5:
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1) {rsn = modify, FRN = yFRN, parentFRN = cFRN, filename = y.txt}
2) {rsn = rename-old, FRN = bFRN, parentFRN = aFRN, filename = b}
3) {rsn = rename-new, FRN = bFRN, parentFRN = rFRN, filename = b}
=
4) {rsn = modify, FRN = yFRN, parentFRN = cFRN, filename = y.txt}
5. 5) {rsn = delete, FRN = aFRN, parentFRN = root, filename = a}
In addition from the foregoing example, the state of the relevant production
server 105
volume at the time of replication is shown as "C: \p\q\r\b\c\y.txt."
[0052] In order to send changes for record 1 to backup server 110 in this
particular
example, production server 105 needs to retrieve the file path for "y.txt"
from backup
server 110. Specifically, due to the above-described path change, the path for
"y.txt" at
production server 105 in the snapshot for "c-FRN" is C:\p\q\r\b\c\y.txt, which
is different
from its path at backup server 110 (i.e., C: \a\b\c\y.txt). Implementations of
the present
invention can solve this issue with at least two alternative approaches. In
one
implementation, for example, the USN journal can simply retrieve and store
path metadata
from backup server 110 in a relational database, and thus continually
correlate file paths at
production server 105 and backup server 110.
[0053] In an alternative implementation, production server 105 can scan the
USN journal
twice. In the first pass, production server 105 can correlate this information
through
iterative scans (or "passes") of USN journal 140. In one scan, for example,
production
server 105 caches each folder rename. In a second pass, production server 105
can
compute the corresponding path at backup server 119 based on the cached
renames and
current paths. For example, at the end of a first pass, production server 105
might cache
the following information about deleted and/or renamed directories:
{FRN = bFRN, replica_parent = aFRN, replica name = b}
{FRN = aFRN, replica_parent = root, replica name = a}
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To compute the file path for y.txt, production server 105 first identifies
that the parent
FRN (i.e., "File Reference Number") for y.txt in record "1" is cFRN. In a next
step,
production server 105 computes the file name for cFRN, as well as the file
name of the
parent FRN. Production server 105 then looks in cache before querying the file
system.
Since, in this example, the cache has no file name entry for the parent cFRN,
production
server 105 queries the file system, and determines that the file name is c,
and that the
parent is bFRN.
[0054] Production server 105 then computes the file name of bFRN, as well as
bFRN's
corresponding parent file name. As before, production server 105 first looks
before
querying the file system. Since the cache has an entry for bFRN in this
example,
production server 105 determines that the file name is b, and that the parent
is aFRN.
Production server then computes the file name of aFRN and the parent file name
of aFRN.
Again, production server 105 first looks at the cache before querying the file
system, and
since the cache has an entry for aFRN in this example, production server 105
determines
that the file name of aFRN is "a," and the parent FRN is "root."
[0055] Ultimately, production server 105 computes the final path as
"c:\a\b\c\y.txt." Next,
when record 3 (rename-new) is processed in the second pass, the cache is
updated for the
new parent file name as follows.
{FRN = bFRN, replica_parent = rFRN, replica name = b}
{FRN = aFRN, replica_parent = root, replica name = a}
When production server 105 processes record 4, even though the record is
identical to
record 1, the path computed for y.txt is now "C:\p\q\r\b\c\y.txt.". The
computed path is
different in this particular case since the parent "bFRN" in the cache is now
"rFRN."
Accordingly, the foregoing text illustrates how the two-pass algorithm can
help optimize
the amount of data that production server 105 transfers to backup server 110.
In
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particular, the foregoing text describes multiple ways in which production
server 105 can
identify at the time of the second pass any created files, as well as any
files that are
modified and then deleted, and thus properly correlate file paths with backup
server 110.
[0056] Accordingly, Figures 1A-1B arid the corresponding text provide a number
of
systems, components, and mechanisms for efficiently backing up a production
server's
data in a virtually continuous fashion. In addition to the foregoing,
implementations of the
present invention can also be described in terms of flowcharts of methods
having a
sequence of acts for accomplishing a particular results. In particular, Figure
2 illustrates
flowcharts of from the perspective of production server 105 and backup server
110 in
accordance with implementations of the present invention for backing up and
recovering
data. The acts illustrated in Figure 2 are described below with respect to the
components
and diagrams illustrated in Figures 1A-1B.
[0057] As a preliminary matter, reference is sometimes made herein to a
"first," "second,"
or "third" event (or an "instance") in a sequence of time. One will
appreciate, however,
that such designations are merely to differentiate unique instances on a
continuum, such
that the "first" event or instance is not only different from a "second" or
"third" instance,
but also occurs at some point before the "second" and/or "third" instances.
For example,
the creation and sending of a baseline "full" copy of data (e.g., 45) could
also be
considered a second or third (or later) instance with respect to some prior
event (not
shown), even though described primarily as a first instance with respect to
update 150.
Similarly, update 150 could be described as a occurring at a "first" instance
in time with
respect to update 155 (e.g., a "second" instance), and so forth, though these
terms are
primarily described herein as "second" and "third" instances of times in the
illustrated
examples with respect to baseline full 145. Such term usage in the relative
sense for
sequential events also applies to usage herein of the terms "initial" or
"subsequent."
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[0058] For example, Figure 2 shows that a method from the perspective of
production
server 105 of replicating production server data in a virtually continuous,
application (i.e.,
or file system)-consistent fashion, such that recent data can be easily
recovered from the
backup server, comprises an act 200 of sending a consistent copy of volume
data to a
backup server. Act 200 includes sending a copy of volume data from a
production server
to a backup server, wherein the data are consistent for a first instance of
time. For
example, production server 105 (e.g., in response to replica agent or other
command from
backup server 110) creates an entire volume backup 145 that is consistent for
a particular
point in time (e.g., "to"). In one implementation, this involves calling, all
application
writers at production server 105 to freeze and begin preparations for backup.
Production
server 105 then copies all data on the volume (or on specific files, folders,
or file-types,
etc.), and prepares this data to be sent to (and stored at) backup server 110.
[0059] Similarly, Figure 2 shows that the method from the perspective of
backup server
110 of replicating production server data in a virtually continuous,
consistent fashion, such
that recent data can be 'easily recovered from the backup server, comprises an
act 240 of
receiving an consistent volume backup from a production server. Act 240
includes
receiving one or more volume backups from a production server, wherein the one
or more
volume backups are consistent (i.e., application or file system-consistent)
for an initial
instance of time. For example, Figure 1A shows that backup server 110 receives
and
stores full backup 145, which is received over a network from production
server 105, or
received from a tape drive or other storage node that is at some point
connected with
backup server 110. In particular, a backup administrator can take a hardware
snapshot of
production server 105, and then attach the snapshot to backup server 110.
[0060] In addition, Figure 2 shows that the method from the perspective of
production
server 105 comprises an act 210 of identifying one or more changes to the
volume data.
24
CA 02649404 2012-04-26
51007-78
Act 210 includes identifying one or more changes to the volume data via one or
more
volume log files. For example, as shown in Figures 1A and 1B, volume filter
driver 115
can track changes to files 120, 125, and 130 and store those changes in volume
log file
135. In one implementation, these one or more changes may alternatively be
stored in
memory 170 as in-memory bitmaps before being placed in volume log file 135.
[00611 Figure 2 also shows that the method from the perspective of production
server 105
comprises an act 220 of saving one or more consistent updates to disk. Act 220
includes,
upon identifying a replication cycle event, saving the one or more data
changes in the one
or more volume log files, wherein the one or more data changes are consistent
for a second
instance of time. For example, upon identifying a replication cycle trigger
(e.g., from a
replica agent), volume filter driver passes bitmaps 193, 195 in memory
allocation 190a to
allocated physical disk space 190b (e.g., also corresponding with volume log
file 135).
This physical disk allocation 190b thus comprises a snapshot for one point-in-
time that is
different from the snapshot 187 stored in disk allocation 185b (i.e., "all
bitmaps" 187).
00621 Furthermore, Figure 2 shows that the method from the perspective of
production
server 105 comprises an act 230 of sending a copy of the consistent updates to
the backup
server during replication. Act 230 includes sending to the backup server a
copy of the one
or more data changes, such that the backup server has a copy of the data that
are valid for
a first instance of time and a second instance of time. For example, in
addition to passing
full update 145 to backup server 110, production server also sends consistent
snapshot
updates 150 and 155, which are each valid for different points in time (i.e.,
"ti," "t2," etc.).
[00631 Accordingly, Figure 2 shows that the method from the perspective of
backup
server 110 comprises an act 250 of receiving one or more consistent updates.
Act 250
includes receiving one or more consistent backup updates, at least one of
which is a
consistent update to at least one of the one or more volume backups for a
subsequent
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instance of time. For example; backup server 110 receives any of consistent
snapshot
updates 150, 155, such that backup server now has data copies for various
incremental
points in time (i.e., "t1," "t2," etc.) compared to fall backup 145 ("to," or
some other
baseline full).
[0064] In addition, Figure 2 shows that the method from the perspective of
backup server
110 comprises an act 260 of receiving a recovery request. Act 260 includes
receiving a
recovery request for data that are valid in accordance with the subsequent.
instance of time.
For example, backup server 110 receives a request (not shown) for a particular
file that is
valid for time "t1," which is a file found in both baseline full backup 145
and update 150.
Furthermore, Figure 2 shows that the method from the perspective of backup
server 110
comprises an act 270 of identifying the requested data valid for the
subsequent instance in
time. Act 270 includes identifying the requested data for the subsequent
instance of time
at one or more backup server volumes, wherein the requested data include at
least a
portion of the at least one consistent backup update.
[0065] With respect to database data, for example, backup server 110 might
roll together
copies of the file at each preceding and current point in time that is valid
for the request;
that is, backup server 110 combines copies of the file from times "to," and
"ti." On the
other hand with file system data, each subsequent update (e.g., 150, 155) may
include a
full, updated copy of the requested file, and, as such, backup server 110 may
only need to
identify the requested data in the most recent update (or some other
subsequent update) for
the requested point-in-time. Thus, depending on the type of data requested,
backup server
110 may need to identify each incremental update from the point requested
going back to
the latest baseline full, or may need to simply identify the requested data in
the latest
point-in-time update.
= 26 =
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[0066] As such, Figure 2 also shows that the method from the perspective of
backup
server 110 comprises an act 280 of returning the requested data. Act 280
includes sending
the requested data that is valid for the subsequent instance Of time to the
production server.
For example, with the case of database data, backup server 110 provides
recovery 160,
which includes both baseline full data (e.g., 145) as well as incremental
update data (e.g.,
150, 155), while with file-system data, backup server 110 provides a recovery
that has at
least the file data from the requested update point-in-time. Backup server's
110 response
160 can also be an indication for which recovery time the response is valid.
As shown in
Figure 1A, recovery data 160 shows that the data are valid for time "t1."
[0067] Accordingly, the diagrams, components, and methods in accordance with
implementations of the present invention provide a number of advantages over
conventional backup systems. In particular, implementations of the present
invention
provide ways of backing up data that are data source agnostic (e.g., via
volume filter
driver 115), do not necessarily require a version of the application running
on a backup
server, and represent virtually continuous replication. As previously
described, these
optimizations are based at least in part on tracking or monitoring changes
with low
overhead at a volume level using a volume filter driver (e.g., 115), and also
performing
replication cycles at the file level using, for example, a USN journal, so
that file-level
inclusions/exclusions can still be applied.
100681 In addition, implementations of the present invention provide for the
creation of
full baseline copies of the production server data at a backup server in an
optimized
manner, and without necessarily requiring transferring the full data across a
network.
Minimizing the amount of subsequent data that are transferred to a backup
server can
provide a substantial reduction in the potential resource drains on the
network and on the
production servers. As such, implementations of the present invention further
provide a
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number of alternative ways ,for meeting stringent recovery time objectives.
Implementations of the present invention also provide a number of ways for
tracking data
changes (e.g., byte or byte block level) with low performance overhead, and
tracking data
changes in a manner that is independent of the file system and
hardware/software
snapshots. Furthermore, implementations of the present invention also provide
one or .
more ways to reconstruct path information (such as with USN-based replication)
without
necessarily requiring persistent state on the relevant production servers.
[0069] The embodiments of the present invention may comprise a special purpose
or
general-purpose computer including various computer hardware, as discussed in
greater
detail below. Embodiments within the scope of the present invention also
include
computer-readable media for carrying or having computer-executable
instructions or data
structures stored thereon. Such computer-readable media can be any available
media that
can be accessed by a general purpose or special purpose computer.
[0070] By way of example, and not limitation, such computer-readable media can
comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk
storage or other magnetic storage devices, or any other medium which can be
used to carry
or store desired program code means in the form of computer-executable
instructions or
data structures and which can be accessed by a general purpose or special
purpose
computer. When information is transferred or provided over a network or
another
communications connection (either hardwired, wireless, or a combination of
hardwired or
wireless) to a computer, the computer properly views the connection as a
computer-
readable medium. Thus, any such connection is properly termed a computer-
readable
medium. Combinations of the above should also be included within the scope, of
computer-readable media.
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[00711 Computer-executable instructions comprise, for example, instructions
and data
which cause a general purpose computer, special purpose computer, or special
purpose
processing device to perform a certain function or group of functions.
Although the
subject matter has been described in language specific to structural features
and/or
methodological acts, it is to be understood that the subject matter defined in
the appended
claims is not necessarily limited to the specific features or acts described
above. Rather,
the specific features and acts described above are disclosed as example forms
of
implementing the claims.
[0072] The present invention may be embodied in other specific forms without
departing
= from its essential characteristics. The described embodiments are to be
considered in all respects only as illustrative and not restrictive. The scope
of the
invention is, therefore, indicated by the appended claims rather than by the
foregoing
description. All changes which come within the meaning and range of
equivalency of the
claims are to be embraced within their scope.
29 =
